In a twin clutch type automatic transmission in which forward first speed to forward eighth speed gear positions and a reverse gear position can be established, an arrangement in which when establishing the forward second speed gear position and when establishing the reverse gear position a second speed output gear 48b provided on a second output shaft 22 is shared, when establishing the forward second speed gear position the driving force is transmitted from a second speed input gear 48a provided on a second input shaft 18 to the second speed output gear 48b, and when establishing the reverse gear position the driving force is transmitted from an idler gear 60 provided on a second countershaft (idle shaft) 26 to the second speed output gear 48b is known from Patent Document 1 below.    Patent Document 1: Japanese Patent Application Laid-open No. 2008-69832